1. Field of the Invention
The present invention relates to magnetic locks for cabinets and other compartments or enclosures, including earthquake locks for cabinets using magnets.
2. Description of the Prior Art
Earthquakes are inevitable in many parts of the world, and can be a constant potential hazard that some persons must live with on a daily basis. Many earthquakes, however, are not catastrophic events. Nonetheless, minor or moderate earthquakes may still cause damage as items are thrown off shelves and contents of closed cabinets or other enclosures are discharged. Some cabinets have doors with locks that can help prevent damage to the contents of the cabinets if the doors remained closed or locked during such earthquakes.
For example, U.S. Pat. No. 5,152,562 teaches a locking device that uses a ball that is held in an elevated position in a housing. At the base of the housing is a latch that attaches to the inside of a cabinet door. The latch has a slot cut into it such that when the door is closed, the slot is positioned under the ball. When an earthquake strikes, if the force is sufficient it causes the ball to be displaced from its resting position and clown into the slot. This can then prevent the door from opening and spilling the contents of the cabinet. However, if the movement that causes the ball to drop also causes the door to fly open before the ball drops into the slot, the lock will not be effective. Indeed, if the door has opened widely enough and the ball drops into the slot, the dropped ball may even block the door from closing again. Also, once the lock is set, additional devices are needed to open the cabinet again. The patent teaches securing a string that passes through the side of the cabinet so that a user can pull the ball back up so that the door can be opened.
Another example is U.S. Pat. No. 5,518,282 that teaches a system that keeps a door or drawer locked on a more continuous basis. The patent discloses a hooked shaped latch that hooks onto a ledge attached to the door. There is a release mechanism provided that allows the door to be opened for ordinary use. While this device eliminates the need for a device to lock the door in the event of an earthquake, one of its drawbacks is that it may create inconvenience in accessing the contents of the cabinets on a continuous basis.
Two systems have been developed in Japan as well. JP9067970A2 and JP9078926A2 are directed toward the use of balls to engage latches to prevent doors from opening in the event of an earthquake. JP9067970A2 teaches a system similar to U.S. Pat. No. 5,152,562 in that a ball is designed to drop into a bracket with a slot that is attached to the door. JP9078926A2 teaches a system in which a ball drops down and engages a spring mechanism that causes two pins to laterally move into holes drilled in the doors. Once the pins are in place, the doors will not open. However, in JP9067970A2, if the doors are opened before the ball completes its drop, the ball does not align with the slot in the bracket. Also, in JP9078926A2, the same occurrence can cause the pins not to align with the holes in the doors. Thus, the locks in both of those disclosed inventions can be rendered ineffective by timing in the sequence of events. The present invention seeks to overcome, among other things, some of the problems present in existing systems.